Spray Analysis and Development


Our spray consulting with clients rapidly develops practical solutions to their problems. We uniquely combine analysis and research with the experience of industrial practice. Modeling spray applications is one of the problem solving tools to evaluate and optimize solutions.

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We use a number to tools to analyze spray systems that include experimental spray quantification and computational fluid mechanics. Our approach is to apply the least complex and least costly method to resolve an issue. We provide the experience to select the right tools for the work and the access to up-to-date spray diagnostics including Phase Doppler Particle Analysis, PDPA. Computationally we use modeling simulation tools from MATLAB based to CFD simulations with 5 million grid cells. Our experience allows the most complex tools to be used cost effectively.

Spray technology is used in diverse applications in many industries. Our expertise in applying sprays in chemical and petrochemical processes is based on fluid dynamics fundamentals. We provide unbiased and independent perspective on selection and design considerations for the selection of spray technology and troubleshooting. Sprays are used in many processes for enhancing the rate of heat and mass transfer. Today the term "Process Intensification" is used to describe the cost effective process improvements.

Our expertise includes the design and development of custom nozzle applications.

The selection of a nozzle is a tactical move that influences the outcome, and is certainly more than just "choosing a spray nozzle." Misconceptions often limit how well we practice the art and science of engineering. Without state-of-the-art knowledge of fundamentals and "rules-of-thumb," the technology can be misapplied.

Spiral type spray nozzle- Bete TF nozzle

Single fluid  spray nozzle

Spray Usage: sprays are used for two primary purposes:

The range of drop size in many commercial spray nozzles is ~30 which results in 27,000 of the smallest drops for the same mass as a single large drop.

Units of drop diameter are typically microns ( micrometers) which is equal to 0.001 mm or 1/25400 inch .

Spray nozzle types:

Nozzles are often classified by the source of energy used to create the dispersion of the liquid into drops, atomization.

Single fluid nozzles use the kinetic energy of the liquid itself to cause the formation of drops. This liquid stream is often highly turbulent which causes disruption of the liquid surface. A vast majority of spray nozzles used industrially are hydraulic nozzles. There are hundreds of designs that are commercially available and many sizes of each design. This type of nozzle is the nearly always the most energy efficient at generating drop surface area. Many different spray patterns are available, flat fan, hollow cone, and solid cone.

Flat Fan spray - Left image

Solid cone spray - Right image

Flat fan single fluid spray nozzleSolid cone single fluid spray nozzle

 

Two fluid spray nozzles use the kinetic energy of expanding gas as the energy source to atomize the liquid. This also provides a second degree of freedom to control spray parameters (drop size ) independent of liquid flow rate. This type of atomizer is the second most common type of spray nozzle. Many designs are customized to specific applications ranging from gas turbine (jet engine) fuel spray to spraying paint.

Rotary nozzles use a high speed rotating plate or cup that “slings” liquid from the outer edge to generate a spray. This nozzle type is used in spray drying and some spray painting.

Ultrasonic atomizers use a high frequency driver (~50 KHz) as the energy source coupled to a liquid discharge surface to cause a fine low velocity spray. This type of nozzle is frequently used where the liquid flow rate is low.

Spray Physics

The physics associated with spray generation and usage is far more complex than many expect. One example is the internal motion of drops, even rain drops!


The plot below is a cross-section showing the relative velocity of the internal circulation pattern developed in a liquid drop moving in a gas. The gas motion, in the horizontal direction, results in a doughnut shaped, toroid, flow within the drop known as a Hill’s vortex. The cause of the internal circulation is the shear force at the drop surface created by the gas moving along the surface. This mixing within drops is important spray technology physics and its understanding is required to properly model spray applications.

Hills Vortex internal drop motion

 

 

 

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